1. Field of the Invention
The subject invention relates to alignment devices and methods and, more particularly, to devices and methods for aligning an antenna with a satellite.
2. Description of the Invention Background
The advent of the television can be traced as far back to the end of the nineteenth century and beginning of the twentieth century. However, it wasn't until 1923 and 1924, when Vladimir Kosma Zworkykin invented the iconoscope, a device that permitted pictures to be electronically broken down into hundreds of thousands of components for transmission, and the kinescope, a television signal receiver, did the concept of television become a reality. Zworkykin continued to improve those early inventions and television was reportedly first showcased to the world at the 1939 World's Fair in New York, where regular broadcasting began.
Over the years, many improvements to televisions and devices and methods for transmitting and receiving television signals have been made. In the early days of television, signals were transmitted via terrestrial broadcast networks and received through the use of antennas. Signal strength and quality, however, were often dependent upon the geography of the land between the transmitting antenna and the receiving antenna. Although such transmission methods are still in use today, the use of satellites to transmit television signals is becoming more prevalent. Because satellite transmitted signals are not hampered by hills, trees, mountains, etc., such signals typically offer the viewer more viewing options and improved picture quality. Thus, many companies have found offering satellite television services to be very profitable and, therefore, it is anticipated that more and more satellites will be placed in orbit in the years to come. As additional satellites are added, more precise antenna/satellite alignment methods and apparatuses will be required.
Modern digital satellite communication systems typically employ a ground-based transmitter that beams an uplink signal to a satellite positioned in geosynchronous orbit. The satellite relays the signal back to ground-based receivers. Such systems permit the household or business subscribing to the system to receive audio, data and video signals directly from the satellite by means of a relatively small directional receiver antenna. Such antennas are commonly affixed to the roof or wall of the subscriber's residence or are mounted to a tree or mast located in the subscriber's yard. A typical antenna constructed to receive satellite signals comprises a dish-shaped reflector that has a support arm protruding outward from the front surface of the reflector. The support arm supports a low noise block amplifier with an integrated feed “LNBF”. The reflector collects and focuses the satellite signal onto the LNBF which is connected, via cable, to the subscriber's television.
To obtain an optimum signal, the antenna must be installed such that the centerline axis of the reflector, also known as the “bore site” or “pointing axis”, is accurately aligned with the satellite. To align an antenna with a particular satellite, the installer must be provided with accurate positioning information for that particular satellite. For example, the installer must know the proper azimuth and elevation settings for the antenna. The azimuth setting is the compass direction that the antenna should be pointed relative to magnetic north. The elevation setting is the angle between the Earth and the satellite above the horizon. Many companies provide installers with alignment information that is specific to the geographical area in which the antenna is to be installed. Also, as the satellite orbits the earth it may be so oriented such that it sends a signal that is somewhat skewed. To obtain an optimum signal, the antenna must also be adjustable to compensate for a skewed satellite orientation.
The ability to quickly and accurately align the centerline axis of antenna with a satellite is somewhat dependent upon the type of mounting arrangement employed to support the antenna. Prior antenna mounting arrangements typically comprise a mounting bracket that is directly affixed to the rear surface of the reflector. The mounting bracket is then attached to a vertically oriented mast that is buried in the earth, mounted to a tree, or mounted to a portion of the subscriber's residence or place of business. The mast is installed such that it is plumb (i.e., relatively perpendicular to the horizon). Thereafter, the installer must orient the antenna to the proper azimuth and elevation. These adjustments are typically made at the mounting bracket.
One method that has been employed in the past for indicating when the antenna has been positioned at a proper azimuth orientation is the use of a compass that is manually supported by the installer under the antenna's support arm. When using this approach however, the installer often has difficulty elevating the reflector to the proper elevation so that the antenna will be properly aligned and then retaining the antenna in that position while the appropriate bolts and screws have been tightened. The device disclosed in U.S. Pat. No. 5,977,922 purports to solve that problem by affixing a device to the support arm that includes a compass and an inclinometer. In this device, the support arm can move slightly relative to the reflector and any such movement or misalignment can contribute to pointing error. Furthermore, devices that are affixed to the support arm are not as easily visible to the installer during the pointing process. In addition, there are many different types and shapes of support arms which can require several different adapters to be available to the installer. It will also be understood that the use of intermediate adapters could contribute pointing error if they do not interface properly with the support arm.
Another method that has been used in the past to align the antenna with a satellite involves the use of a “set top” box that is placed on or adjacent to the television to which the antenna is attached. A cable is connected between the set top box and the antenna. The installer initially points the antenna in the general direction of the satellite, then fine-tunes the alignment by using a signal strength meter displayed on the television screen by the set top box. The antenna is adjusted until the onscreen meter indicates that signal strength and quality have been maximized. In addition to the onscreen display meter, many set top boxes emit a repeating tone. As the quality of the signal improves, the frequency of the tones increases. Because the antenna is located outside of the building in which the television is located, such installation method typically requires two individuals to properly align the antenna. One installer positions the antenna while the other installer monitors the onscreen meter and the emitted tones. One individual can also employ this method, but that person typically must make multiple trips between the antenna and the television until the antenna is properly positioned. Thus, such alignment methods are costly and time consuming.
In an effort to improve upon this shortcoming, some satellite antennas have been provided with a light emitting diode (“LED”) that operates from feedback signals fed to the antenna by the set top box through the link cable. The LED flashes to inform the installer that the antenna has been properly positioned. It has been noted, however, that the user is often unable to discern small changes in the flash rate of the LED as antenna is positioned. Thus, such approach may result in antenna being positioned in an orientation that results in less than optimum signal quality. Also, this approach only works when the antenna is relative close to its correct position. It cannot be effectively used to initially position the antenna. U.S. Pat. No. 5,903,237 discloses a microprocessor-operated antenna pointing aid that purports to solve the problems associated with using an LED indicator to properly orient the antenna.
Such prior antenna mounting devices and methods do not offer a relatively high amount of alignment precision. Furthermore, they typically require two or more installers to complete the installation and alignment procedures. As additional satellites are sent into space, the precision at which an antenna is aligned with a particular satellite becomes more important to ensure that the antenna is receiving the proper satellite signal and that the quality of that signal has been optimized. It is also desirable to have an antenna alignment device that can be effectively used by one installer.
There is a need for a method for aligning an antenna with a satellite that can be employed in connection with a set top box and that can be quickly, accurately, and efficiently employed by one installer.